The facilities standards of water supply' issued by the Ministry of Environment in 2004 indicates that expansion joints cannot be used in welding water supply steel pipes. However, their reason is not clear and it is difficult to confirm the stability of the steel pipe for a water supply pipeline. The purpose of this study is to determine whether or not an expansion joint is necessary to improve the stability of water supply in steel pipe through a displacement analysis of the pipework. The

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... results are as follows. Firstly, it was found that expansion and contraction of the water supply steel pipe (D 2,400 mm) occur repeatedly in 4 cycles per year, and the maximum expansion and contraction amount of the pipe is 13.03 mm in 1.24 km pipelines. Secondly, the thermal stress caused by expansion and contraction of the steel pipe is 13.7~36.1kgf/cm 2 according to the burial depth (0~4 m). The main comparison factors to determine the stability of the steel pipe (STWW 400) were the allowable tensile strength and the fatigue limit, which were computed to be 4,100 kgf/cm 2 and 1,840 kgf/cm 2 , respectively. Finally, the thermal stress of the steel pipe is very small compared to the allowable tensile stress and fatigue stress. Therefore, thermal stress does not affect the stability of the steel pipe, although the expansion and contraction of the steel pipe occurs by temperature changes. In conclusion, the study demonstrated that expansion joints are not required in water supply steel pipelines. 발생되는 온도응력은 매설깊이(최대 4 m)에 따라 13.7~36.1 kgf/cm 2 로 발생되며, 강관(STWW 400)의 안정성에 큰 영향을 키치는 주요 비교인자인 허용 인장강도 와 피로한도는 4,100 kgf/cm 2 와 1,840 kgf/cm 2 로 산출되었다. 마지막으로, 수도용 강관의 온도응력은 허용 인장강도와 피로한 도와 비교시 매우 작음에 따라, 온도변화에 의한 관로의 신․수축이 발생하여도 관로 안정성에는 영향을 끼치지 못함을 알 수 있었다. 결론적으로 금번 연구를 통하여 수도용 강관의 관로부에는 신축이음관을 설치할 필요가 없는 것으로 증명되었다.